<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>

        *{
            margin: 0;
            padding: 0;
        }
        .header{
            width: 1200px;
            height: 200px;
            background-color: pink;
            margin: 0 auto;
        }
        .main{
            width: 1200px;
            height: 3000px;
            background-color: orange;
            margin: 0 auto;
        }

        .zx{
            position: fixed;
            left: 50%;
            /* 再往右移动版心的一半 */
            margin-left: 600px;
            bottom: 100px;
            width: 200px;
            height: 50px;
            line-height: 50px;
            text-align: center;
            background-color: red;
        }
    </style>
</head>
<body>
    <div class="header">

    </div>
    <div class="main">

    </div>
    <div class="zx">
        咨询
    </div>
</body>
</html>